The communication device, which performs wireless or wired information communication, includes various high-frequency components such as an amplifier, a mixer, and a filter. Among them, a band-pass filter (BPF) has a function to allow only a signal in a necessary certain frequency band (desired wave) to pass. A band pass filter is formed by arranging a plurality of resonance elements. On the other hand, a band-rejection filter (BRF) has a function to attenuate a certain frequency (undesired wave) to inhibit a certain signal from passing.
In a recent wireless system in which a plurality of systems are adjacent to each other on a frequency axis and different frequencies are sometimes used in transmission and reception, the various filters are combined to limit a band and remove spurious. To meet needs for a small sized communication device, a smaller filter is desired.
JP-A 2009-77330 (KOKAI) discloses the high-frequency filter obtained by combining the band-rejection filter and the band-pass filter.